Abstract

The production of dendritic cells (DC) from haemopoietic progenitors maintained in long
term stroma-dependent cultures (LTC) of spleen or bone marrow (BM) occurs independently
of added granulocyte/macrophage colony stimulating factor (GM-CSF). The possibility that
cultures depend on endogenous GM-CSF produced in low levels was tested by attempting to
generate LTC from spleen and BM of GM-CSF-/- mice. Multiple cultures from GM-CSF-/-
and wild type mice were established and compared for cell production. GM-CSF-/- LTC
developed more slowly, but by 16 weeks produced cells resembling DC in numbers comparable
to wild type cultures. LTC maintained distinct populations of small and large cells, the latter
resembling DC. Cells collected from GM-CSF-/- LTC were capable antigen presenting
cells (APC) for T cell stimulation and morphologically resembled DC. Large cells expressed
the CD11b, CD11c, CD86, 33D1 and Dec-205 markers of DC. Addition of GM-CSF to
GM-CSF-/- LTC increased the proportion of large, mature DC present in culture. Stromal cells
from GM-CSF-/- LTC could support the differentiation of DC from early progenitors maintained
in LTC without addition of GM-CSF. However, GM-CSF is not a critical factor in the invitro generation of DC from progenitors. It can, however, substitute for stromal cells in
increasing the survival of mature DC.